I. Field of the Invention
This invention relates to hydrocarbon conversions involving catalytic cracking. It also relates to magnetic separation of metal contaminated cracking catalysts such as disclosed in U.S. Pat. No. 4,406,773 of W. P. Hettinger, Jr. and R. M. Benslay, and U.S. Pat. No. 4,359,379 of Nippon Oil Company.
II. Description of the Prior Art
U.S. Pat. No. 4,591,425 to S. M. Kovach and C. M. Miller discloses the desirability of making use of cracking catalyst from a fluid catalytic cracking unit to convert increasingly more metal contaminated hydrocarbon feeds. Broadly, for purposes of this specification and claims, the term "hydrocarbyl" feed shall mean a petroleum feedstock characterized as follows: % by weight of hydrogen in the range of 6-18%; of carbon in the range of 67-94%; of metal contaminates comprising nickel, cobalt, magnesium, vanadium, and sulfur in the range of 0-15%; any other typical characteristic that is used to characterize crude like viscosity, etc.; and a Conradson carbon number in the range 0-30%. "FCC" shall mean throughout this specification fluid catalytic cracking as further defined in the Petroleum Handbook. Catalytic cracking is defined and described in Shreve's Chemical Process Industries, 5th ed., by George T. Austin, Chapter 37, pp 735-740. Catalytic cracking is also defined and described in Petroleum Refining Technology and Economics, 2nd ed., by James H. Gary and Glenn E. Handwerk, Chapter 7, pp 99-108.
U.S. Pat. No. 4,359,379 to Ushio et al. (Dec. 16, 1980), assigned to Nippon Oil Company, Ltd., discloses a process for fluid catalytic cracking of distillation residual oils. A part of the catalyst particles are withdrawn in a stream of a carrier fluid consisting of air, nitrogen, or steam and mixtures thereof, at a rate of 0.01 to 100 meters/second in a particle concentration of 0.01 to 500 grams/liter to a high gradient magnetic separator. A ferromagnetic matrix is placed in a uniform high magnetic field to generate a high magnetic gradient around the matrix, thereby separating the withdrawn particles into a group of particles rendered magnetic by the deposition of nickel, vanadium, iron, and copper. These metals were contained in the starting oil. The non-magnetic particles are returned to the fluid catalytic cracking unit for re-use.